Bruxism is the most frequently occurring oral movement disorder, and psychological factors and pathophysiological factors have been suggested as its etiologies . Because the complications of bruxism, such as tooth wear, masticatory muscle pain, and insomnia significantly impairs the quality of life, prompt treatment is required. However, only a few controlled studies have been conducted for examining the effect of therapeutic agents . Among antidepressants, amitriptyline and selective serotonin reuptake inhibitors (SSRIs) may exacerbate sleep bruxism . On the other hand, there have been no data regarding the efficacy of other antidepressants including mirtazapine on bruxism . In our patient, mirtazapine was effective for suppressing side effects of chemotherapy as well as bruxism. The effect of mirtazapine in the treatment of bruxism is related to unique mode of biochemical CNS action . In fact, Mirtazapine increases dopaminergic neurotransmission in the prefrontal cortex by (1) 5-HT2A and 5-HT2C receptors blockade, (2) 5-HT1A receptor activation, and (3) an elevation in noradrenaline levels, which may contribute to the effect in our patient [12, 13]. This subject further reinforces the dopamine dysregulation hypothesis in the pathogenesis of bruxism .
In conclusion, mirtazapine was effective for treating bruxism as well as chemotherapy complications. However, wider investigations are necessary in this field through randomized controlled trials.